Question

Why is it generally more severe to be burnt by steam at 100°C than by boiling water at 100°C?

• A. Steam contains more latent heat of vaporization,
• B. Steam has a higher specific heat capacity.
• C. Steam molecules are moving faster.
• D. Steam is hotter than boiling water.

Answer 1

Answer:

A. Steam contains more latent heat of vaporization,

• Phase Transition Dynamics: While both steam and boiling water exist at 100°C, steam is in a gaseous state while water is in a liquid state. Steam possesses additional energy known as Latent Heat of Vaporization.
• Latent Heat Value: At standard atmospheric pressure, the latent heat of vaporization for water is approximately 2260 kJ/kg. This is the energy required to convert 1 kg of boiling water into steam at the same temperature.
• Energy Release upon Condensation: When steam comes into contact with human skin, it undergoes an exothermic phase change, turning back into liquid water at 100°C. During this process, it releases the stored latent heat directly onto the skin in addition to the kinetic energy of its temperature.
• Comparison of Impact: Boiling water at 100°C transfers heat only through convection and conduction based on its thermal energy. Steam transfers this same thermal energy plus the massive amount of latent energy released during condensation, leading to significantly deeper and more severe tissue damage.
• Relevant Physical Principles: This phenomenon is governed by the First Law of Thermodynamics regarding energy conservation. In competitive examinations, it is essential to note that steam acts as a 'high-energy reservoir' compared to liquid water at the same temperature due to this phase-change energy.